Binary Optic Components ("BOCs") are complex diffraction gratings and function based on the particular well known phenomenon of diffraction of light. As those skilled in the art will appreciate, any incoming light beam incident on a complex diffraction grating is diffracted (e.g., see FIG. 4, where diffraction grating 130 diffracts an input beam), with the characteristics of the resulting output beam(s) dependant upon the characteristics of the particular grating. In principle, any desired optical beam distribution can be computer coded and reproduced in terms of diffraction gratings using electron beam write up techniques. Subsequently, these grating patterns can be processed using semiconductor processing technology in order to increase the diffraction grating efficiency. When the resulting processed components are illuminated with light beams, the desired output distribution is obtained. In the past, design and fabrication of BOCs has been used for applications such as testing optical components and generation of complex optical distributions.
Relative to the present invention, the most significant application of BOCs is the fact that several different miniaturized BOCs can be fabricated on a single substrate, with a high degree of accuracy. It has been found that the overall miniaturized BOCs may be fabricated so as to be identical to one another, to differ from one another, or to include groups of differing miniaturized BOCs. The resulting overall component is referred to herein as a miniaturized array element BOC. The present invention includes several methods of utilizing these miniaturized array element BOCs, including splitting, scanning, and/or collecting light beams.
First, a beam splitter is used to divide a light beam into two or more optical beams with identical or differing properties. An input light beam can normally be split into two (2) output beams with the help of a single partially reflecting (or transmitting) mirror or prism (e.g., see FIGS. 5A and 5B). A combination of several of these components can be used to split the input beam into several output beams (e.g., see FIG. 5C). A polarization beam splitter may be used to divide an input beam based on the polarization characteristics. On the other hand, light beams may be split into several beams using a diffraction grating into "different diffraction orders."
Each of the foregoing processes for splitting beams, however, are limited in several ways. For example, these methods are characterized by being complex; being bulky (i.e., requiring several optical elements with optical coatings); having limited control on output beam intensities (i.e., for diffraction orders); and tending to be very expensive. The present invention addresses the problems associated with these devices by utilizing, among other things, an optic array beam splitter ("OABS"), comprised of miniaturized array element BOCs.
Second, a "scanned" beam can be defined as a beam whose direction and/or location is changing over time. Such changes may or may not be repetitious or cyclic. There are several known ways for scanning a light beam. The most simple technique consists of a simple motorized or mechanized rotating mirror. In this example, an input light beam reflected off of the rotating mirror would exit in a different direction, based on the orientation of the rotating mirror at a particular time. There are several other techniques and components which may be used for scanning. Some of the techniques consist of: acousto-optic or electro-optic Bragg diffraction gratings, while some of the commonly used components used for scanning are: prisms, and holographic optical elements. However, these techniques each suffer from drawbacks. For example, Bragg diffraction gratings based scanners are, in general, limited to one-dimensional scanning, are less efficient, and are expensive. Other commonly used scanners such as prisms, mirrors and holograms are bulky and require precise, expensive motors. Furthermore, a single mirror or prism is limited to one dimensional scanning.
The present invention addresses the foregoing drawbacks associated with the prior art by utilizing, among other things, an optical array sensor transmitter ("OAST") comprised of miniaturized array element BOCs. Although the scanning of a single light beam using BOC arrays in one dimension has been reported in the literature (e.g., William Goltas and Michael Holz, SPIE Vol. 1052, 131-41 1989), the present invention utilizes the process of using an array of optical components such as BOCs, to scan: i) multiple beams in one and/or two dimensions, and ii) a single beam in two dimensions.
Third, many devices such as RADARs and bar code readers, illuminate or intercept targets of mutual interest (i.e., an aircraft or a bar code) with "scanned" radio waves or laser beams, and collect the subsequent reflected or scattered waves or beams ("return beams") to determine the characteristics of the target of interest. These return beams are generally collected in one of two manners.
The first manner is a stationary/non-scanning receiver. The return beams of this first type are normally collected using a large aperture system and focused on a one-dimensional or two-dimensional detector array, depending upon a one dimensional or two dimensional transmitted scan beam. Use of this method requires that each element of the detector array corresponds to a different direction of the transmitted scanned beam. Thus, the main disadvantage of this approach is that it requires a large array of detector elements to capture several directions of the transmitted beam. Furthermore, the receiver is generally suitable for one transmitted scan beam only.
The second manner is a scanning receiver. Here the receiver scans in-sync with the transmission scanning, and normally shares the scanning components with the transmitted beam. As a result, the return beam encounters "positive" (while being transmitted) and "negative" (during return path) scan, resulting in a null scan, and hence the location of return beam is independent of the scanning.
There are two major disadvantages of this approach. First, since the aperture of the receiving optics is normally significantly larger than the transmitter, the null scan option requires that the size of the transmission optics (including the scanning components) be very large, resulting in heavy and costly systems. Second, for multiple beam scans the return beam encounters both the compensating negative scan and compensating de-splitting. Thus, the beam is recombined into a single beam, resulting in only a single return beam. This is undesirable, since multiple beam information in the receiver mode is needed. Therefore, in an optimum system for these applications, compensation (or the negative scan) should be accomplished without sharing the transmitter and receiver apertures, and the receiver beam (or the return beam) should not encounter the de-splitting device or be recombined into a single beam.
Therefore, there arises a need for an optical array constructed which can split, scan and collect a beam of light, either collectively or individually. Additionally, the optical array should preferably be constructed of elements which can be fabricated in a single device. By doing so, the device may be constructed robustly and at great efficiencies. Further, the calibrating and adjusting of such a system is greatly reduced. The present invention directly addresses and overcomes the shortcomings of the prior art.